South Korea and U.S. warships participate in a joint military drill in South Korea's East Sea on March 19. / Yonhap via AP

by Tom Vanden Brook, USA TODAY

by Tom Vanden Brook, USA TODAY

WASHINGTON -- The Pentagon's deployment in the last week of its most advanced fighters, bombers and warships to counter North Korea's mounting threats has overshadowed its more gradual buildup of forces in the region.

Over the last year, the military has responded to the Obama administration's "pivot" to Asia as it withdraws troops from Afghanistan and its war in Iraq recedes into history. The rebalancing of forces addresses, in part, the rise of Chinese power in the region. Other changes were made with a clear focus on North Korea.

Some of the changes include:

â?¢ On Wednesday, the Pentagon announced its intent to sell upgrades to the South Korean military for 60 F-15 fighters already being purchased. The upgrades include advanced radar systems and sniper targeting equipment on the warplanes, which will replace its aging fleet of F-4 aircraft, according to the Pentagon.

â?¢ The military also announced Wednesday it was sending a missile defense system to the Pacific island of Guam to bolster defense against North Korea. The Terminal High Altitude Area Defense System (THAAD) ballistic missile defense system "is a land-based missile defense system that includes a truck-mounted launcher, a complement of interceptor missiles, an AN/TPY-2 tracking radar, and an integrated fire control system," the Pentagon announcement said.

It's the first deployment of the missile-defense system, said Lt. Col. Peggy Kageleiry, an Army spokeswoman. It is one of two in existence, both of them based at Ft. Bliss in Texas.

The Army plans to develop six of the systems, which require about 95 soldiers to operate. It will take a few weeks for the system to reach Guam.

â?¢ Last fall, the Pentagon began shipping Mine Resistant Ambush Protected (MRAP) trucks to South Korea. The vehicles, by the Pentagon's count, have saved the lives of thousands of troops in Iraq and Afghanistan from roadside bombs and presumably would offer similar protection in North Korea should U.S. forces need to travel on its roads.

â?¢ B-1 bomber pilots based at Dyess Air Force Base in Texas are spending more time training for long flights over the Pacific and spending less preparing for attacks in the deserts and mountains of Afghanistan.

â?¢ Hundreds of Marines have been training in the tropical port of Darwin, Australia, since mid-2012.

On Tuesday, North Korea ratcheted up the threats further, announcing that it will restart a reactor it had closed in an arms-control agreement. That follows a week of bluster that included boasts about attacking targets on U.S. soil. George Little, Pentagon press secretary, told reporters that while a North Korean attack did not appear imminent, the military had a "range of assets to deal with the threat."

Little emphasized that the Pentagon wanted to avoid a confrontation but was prepared to deal with it.

B-2 stealth bombers took part last week in war games with the South Koreans, and on Sunday F-22 fighters landed in South Korea. Two advanced Navy warships capable of shooting down ballistic-missiles prowled waters in the region, Little said.

"We are looking for the temperature to be taken down on the Korean Peninsula," he said.

Defense Secretary Chuck Hagel took a step in that direction Tuesday when he spoke with his Chinese counterpart, Minister of National Defense Gen. Chang Wanquan.

Little provided this account of their conversation: "The secretary emphasized the growing threat to the U.S. and our allies posed by North Korea's aggressive pursuit of nuclear weapons and ballistic missile programs and expressed to General Chang the importance of sustained U.S.-China dialogue and cooperation on these issues."

Hagel also met Wednesday with a top South Korean diplomat to emphasize the U.S. commitment to its ally.

Meanwhile, the North Korean army said Thursday morning in Korea, which was Wednesday afternoon in Washington, that it had final approval to launch "merciless" military strikes on the United States, involving the possible use of "cutting-edge" nuclear weapons, according to a statement published by the official KCNA news agency.

The rounds of threat-and-response, at least for now, appear to be for show, not playing for keeps, said Peter Singer, director of the Center for 21st Century Security and Intelligence at the Brookings Institution.

"In its toddler-like cries for attention -- there have been some 20 plus threats of war over the last year," Singer said. "In turn, our demonstrations are of what we have in the toolkit if they actually do act out."